The most abundant wavelengths found in sunlight and many artificial bright light sources are those in the green-yellow portion of the spectrum, i.e., 520 nm to 575 nm. In modern poultry houses, artificial illumination may be the only source of light provided to birds; thus, the duration, intensity, and quality of light become important environmental factors, as light influences both reproductive and productive systems in domestic fowl. Light quality can be defined by two criteria: 1) dose intensity, and 2) quality spectra (Andrews and Zimmerman, 1990). In birds from subtropical and temperate latitudes, photostimulation increases egg production, whereas a reduction in photoperiod delays or decreases production. In addition, light intensity plays an important role in rearing birds, mainly because birds need a certain light intensity to be photostimulated (North and Bell, 1990).
The avian eye, similarly to the human eye, is capable of seeing in a narrow part of the light spectrum (up to 760 nm). Apart from the eyes, birds are equipped with active extra-retinal photoreceptors, located in several parts of the brain, which are involved in transduction of photostimulation. As photostimulation of birds is an integral component of sexual maturation and reproductive performance, there have been numerous reports on the effect of different sources (wavelengths) of light on sexual maturation and reproductive performance in birds (see, for instance, Harrison et al., 1970; Scott and Payne, 1937; Ringoen, 1942; Benoit, 1964; and Phogat et al., 1985). For example, in studies using filtered light, increased growth of turkeys was observed when turkeys were exposed to shorter wavelengths (Proudfoot et al., 1979; Gill and Leighton, 1984; Levenick and Leighton, 1988), whereas sexual maturity was stimulated with white or red, but not blue, light (Scott and Payne, 1937). Schonberg (U.S. Pat. No. 4,625,728) discloses that green light (400 to 600 nm) increases the growth rate of very young chickens, including embryos, while near red light (600 to 670 nm) induces maximal sexual development and may improve egg production. However, Jones et al. (1982) found that red light during the prebreeder or breeder periods was not beneficial for egg production.
Siopes (1984a) found no differences in egg production, fertility, or poult weight when hens were exposed to incandescent (IN) or full-spectrum fluorescent (FL) light treatments or when exposed to cool-white or full-spectrum FL light treatments, respectively (Siopes, 1984b). Felts et al. (1990) reported significantly higher hen-day egg production only during the first 10 weeks of the production period for females exposed to sodium vapor (SV) or daylight FL (DF) lights than for those under IN lights. On the other hand, Hulet et al. (1992) found no significant differences in egg production when hens were exposed to SV, DF, or IN lights.
Light intensity is also considered an important characteristic that relates to egg production. In a study comparing filtered-red light with white light at 85 and 160 1xc3x97, Jones et al. (1982) found that at 85 1xc3x97, egg production was equal between the two light sources. However, at 160 1xc3x97, hens exposed to white light had decreased egg production over those hens exposed to 84 1xc3x97. Pyrzak and Siopes (1986b; 1986c; 1989) examined the effects of equalized (photons/cm2/second) blue, green, and red light on egg quality and oviposition behavior. The authors found no difference in oviposition rate or patterns, but found that red light caused hens to lay heavier eggs with great quantities of albumen per egg. Pyrzak et al. (1987) report that eggs laid under blue or green light were consistently larger then those laid under red light (Pyrzak et al., 1987).
Siopes (1991) reported that light intensity from IN light ranging from 54 to 324 1xc3x97 had no significant effect on reproductive performance of caged turkey hens. Pyrzak and Siopes (1986a) relate that reproductive performance was not different among turkey hens exposed to either IN, blue, green, or red light when the intensity (photons/cm2) remained constant. Felts et al. (1992) disclose that in the presence of a male, female breeder turkeys exposed to a fixed intensity with a DF light source (peak 495-590 nm, green to yellow) or to a SV light source (peak 580 nm, yellow) produced significantly more eggs than those under an IC light source (570 to 700 nm, yellow to red). Rozenboim et al. (1998) exposed prelaying pullets to one of three light treatments: 0.1 or 0.01 W/m2with LED lamps (560 nm, 660 nm or 880 nm) and 0.1 W/m2 mini-fluorescent lamps. They report that a significant reduction in egg production was found in the 880 nm group and that no differences in egg production were found in other groups.
The reproductive efficiency of turkeys is generally low. Thus, turkeys are one example of poultry where the need to enhance reproductive performance is particularly high. One component of this low efficiency is the small amount of egg laying, which is related to a variable propensity toward cessation of egg laying and associated incubation behavior (broodiness). The term xe2x80x9cbroodinessxe2x80x9d describes the behavior and physiological state associated with the maternal care of unhatched eggs. The expression of broody behavior by turkey hens is a costly problem to turkey breeders and producers of hatching eggs, resulting in a substantial loss of egg production.
Thus, what is needed is a method to enhance the reproductive performance of poultry, e.g., egg production in turkeys.
The present invention provides a method to enhance (increase) reproductive performance in poultry. The method comprises exposing one or more poultry during one or more photoperiods, e.g., a plurality of consecutive photoperiods, to one or more light sources so as to enhance the reproductive performance of the poultry. As described herein, retinal photoreceptors of poultry have their maximum sensitivity in the green-yellow part of the spectrum, and these photoreceptors have an inhibitory effect on the gonads. In contrast, the extra-retinal receptors of poultry are stimulated by the red portion of the spectrum (for instance, greater than 630 nm), while the green-yellow part of the spectrum has little or no stimulatory effect on these receptors. Reproductive efficiency in poultry is likely a function of the relative activation or stimulation of extra-retinal photoreceptors and retinal photoreceptors. Therefore, stimulation of the extra-retinal photoreceptors and the lack of stimulation or inhibition of the retinal photoreceptors together contribute to reproductive performance.
Thus, the method of the invention comprises exposing one or more poultry to one or more light sources that emit radiation at one or a plurality of wavelengths (i.e., in a particular spectral region or xe2x80x9cbandxe2x80x9d which does not represent the spectrum emitted by white light) which stimulates gonadal development, preferably by stimulating the extra-retinal receptors, i.e., radiation from 600 nm to 900 nm (inclusive), and radiation at one or a plurality of wavelengths (a band which is not the spectrum emitted by white light) which is not stimulatory or may inhibit gonadal development, preferably by not stimulating or inhibiting the retinal receptors, i.e., from 300 nm to less than 600 nm, each for a period of time so as to result in enhanced reproductive performance in the poultry. Accordingly, the first wavelength of light or band of light is selected as one or a plurality of wavelengths which stimulate gonadal development of the poultry, whereas the second wavelength of light or band of light is selected as one or a plurality of wavelengths which does not stimulate, and may inhibit, gonadal development of the poultry, i.e., the first and second wavelengths or bands are different, e.g., do not overlap. In one embodiment, a single light source with one lamp is employed, e.g., two filters are used in conjunction with the single lamp to provide the two desired bands or wavelengths of light. In another embodiment, a single light source with at least two lamps is employed, wherein one lamp is employed to emit the first band or wavelength of light, and the other lamp is employed to emit the second band or wavelength of light. In yet another embodiment of the invention, at least two light sources are employed. In this embodiment, one light source emits the first band or wavelength of light and a second light source emits the second band or wavelength of light.
The length of the first and second periods of time may be the same or different. In one embodiment, the second period of time is shorter than the first period of time. However, in some circumstances, it may be desirable to expose poultry, i.e., toms, to a band or wavelength of light which is not stimulatory or may inhibit gonadal development for a period of time which is longer than the exposure to a band or wavelength of light which is stimulatory to gonadal development.
Poultry may be exposed to the different bands or wavelengths concurrently or sequentially, in any order. Thus, poultry, during a particular photoperiod, may be exposed to the first band or wavelength of light alone, then to both bands or wavelengths of light, then to the first band or wavelength alone. Alternatively, the poultry may be exposed to both bands or wavelengths of light simultaneously then to the first band or wavelength of light alone, or to the first band or wavelength of light then to both bands or wavelengths of light. In another embodiment, poultry, e.g., toms, may be exposed to the second band or wavelength of light alone, then to both bands or wavelengths of light, then to the second band or wavelength alone, or exposed to both bands or wavelengths of light simultaneously then to the second band or wavelength of light alone, or to the second band or wavelength of light then to both bands or wavelengths of light. However, any combination of selected bands or wavelengths, exposure periods and chronology of exposure of the two different wavelengths or bands, may be employed so long as reproductive performance is enhanced in treated poultry relative to untreated poultry. In one embodiment, photostimulation of poultry with radiation substantially in the red portion of the spectrum, preferably greater than about 630 nm, with limited radiation in the green-yellow portion of the spectrum (preferably 520 nm to 575 nm), results in enhanced reproductive efficiency.
In one preferred embodiment, one or more poultry are exposed during one or more photoperiods to at least two light sources. In any one photoperiod, poultry are exposed to the first light source which emits a first band or wavelength of light which is stimulatory for gonadal development. Then the poultry are simultaneously exposed to a second light source which emits a second band or wavelength of light that is not stimulatory for gonadal development and the first light source. Finally, the poultry are exposed to only the first light source.
The invention further provides a method to enhance reproductive performance in poultry, e.g., turkeys. The method comprises exposing one or more poultry during one or more photoperiods to a first light source which emits substantially red light for greater than 13 hours and to a second light source which emits substantially green-yellow light for less than 11 hours, wherein the poultry are concurrently exposed to red light when they are exposed to green-yellow light. Also provided is a method to enhance reproductive performance in poultry comprising exposing one or more poultry during one or more photoperiods to a light source which emits substantially red light for greater than 13 hours and emits substantially green-yellow light for less than 11 hours, wherein the poultry are concurrently exposed to red light when they are exposed to green-yellow light.
The invention further provides a method comprising exposing one or more poultry during one or more photoperiods to a first light source which emits substantially green-yellow light for greater than 13 hours and to a second light source which emits substantially red light for less than 11 hours, wherein the poultry are concurrently exposed to green-yellow light when they are exposed to red light. Also provided is a method to enhance reproductive performance in poultry, comprising exposing one or more poultry during one or more photoperiods to a light source which emits substantially red light for greater than 13 hours and emits substantially green-yellow light for less than 11 hours, wherein the poultry are concurrently exposed to red light when they are exposed to green-yellow light.
In one preferred embodiment, the use of the method of the invention results in egg production by hens that is enhanced by at least 5%, preferably at least 10%, and even more preferably by at least 15%, relative to hens not subjected to the method.